Hydrostatic drive with direction memory

ABSTRACT

An integrated hydrostatic transmission drive has a manifold attached to a pump drive that interconnects a pair of valves directly mounted on the manifold with the pump and a hydraulic actuator. One of the valves is operable between on-off positions and the second between two directional positions. The second valve is selectively solenoid operated between its positions but detent held in the selected position to act as a direction memory in the event of power cut-off and consequently continues drive of the actuator in the same direction when the power is reactivated. A filter may be provided in the manifold as well as relief valves.

1 1 Sept. 23, 1975 1 HYDROSTATIC DRIVE WITH DIRECTION MEMORY [75] Inventor: James S. Hull, Waterford, Mich.

[731 Assignee: Melvin Corporation, Bay City.

Mich.

[22] Filed: Sept. 26, 1973 [2]] Appl. No.: 400,985

[52] U.S. Cl. 60/403; 60/489; 60/D1G. 10;

91/444; 60/493 [51] Int. Cl. FlSb 15/18 [58] Field of Search 60/453, 468. 465, 473.

60/476, 477, 489. 493. DIG. 2, D10. 10; 91/494, 444, 459. 462, 44s, 44s

3,217,493 11/1965 Kempson et all 60/468 X 3.357.179 12/1967 Gourlay et al. 60/DIG. 10

$369,464 2/1968 Blattry A 91/459 X 3.375.756 4/1968 Bienaime 91/448 X Primary ExaminerEdgar W. Geoghegan Attorney, Agent. or FirmHugh L. Fisher [57] ABSTRACT An integrated hydrostatic transmission drive has a manifold attached to a pump drive that interconnects a pair of valves directly mounted on the manifold with the pump and a hydraulic actuator. One of the valves is operable between on-off positions and the second between two directional positions. The second valve is selectively solenoid operated between its positions but detent held in the selected position to act as a direction memory in the event of power cut-off and consequently continues drive of the actuator in the same direction when the power is reactivated. A filter may he provided in the manifold as well as relief valves.

4 Claims, 3 Drawing Figures HYDROSTATIC DRIVE WITH DIRECTION MEMORY This invention relates to hydrostatic drives and more particularly to hydrostatic drives having integral con trol valve, manifold and pump assemblies.

In order to reduce leakage and destructive contamination entering the various components which make up hydrostatic drives, including a variable displacement pump, a control valve and a hydraulic: actuator, the components are often integrally connected by use of a manifold to which the pump and control valve are directly mounted. The oil is directed to and from the pump, the valve and the actuator by means of passages in the manifold assembly to which the pump and valve are attached. Relief valves may also be attached directly to the manifold.

Where hydrostatic drives are used in industrial appli cations, particularly where they are used to move parts or machine components in opposite directions during a machine cycle, there is sometimes provided a reversing pump having an over center variable displacement. Alternatively, a directional control valve between the pump and actuator which acts to direct fluid to drive the actuator in one direction or the other, may be provided. Where a directional valve is used, it is usually solenoid operated from a centered cut-off position to two operative directional positions. When the power is cut off for one reason or another in the middle of a machine cycle, the valve self-returns to its centered posi tion. At this point it is very important that when the drive continues, the operation is in the same direction. to prevent possible damage to the mechanism. It has been proposed to provide a second valve constituting a manually set memory valve that will keep the direction of the drive in the same direction. When this valve is located near a remote actuator near the machine. the inherent disadvantages of remote separate valves including leakages. difficulty in manual operation, possibility of entry of contamination. etc, become a problem.

It is therefore an object of the invention to provide an integral hydraulic drive system wherein a directional valve will automatically re-establish drive of the actuator in the same direction after a power cut-off and cuton during midcycle operation.

A further object is to provide an integral hydraulic drive system wherein a start-stop valve and a direc tional valve are integrally mounted on and interconnected through a manifold.

These and other objects and advantages will be apparent from the following description and accompany ing drawing in which:

FIG. I is a perspective view of an integral manifold and dual valve assembly;

FIG. 2 is an enlarged schematic and diagramatic view of the various ports and passages in the manifold; and

FIG. 3 is a schematic view of the hydraulic drive system components.

FIG. 3 illustrates the complete drive system which includes a variable displacement pump generally indicated P. having a displacement control I and which is driven by a suitable power source such as an electric motor 3. Directly mounted on the pump is a manifold assembly generally indicated M and which is schemati cally illustrated by the broken line outline in FIG. 3.

A pair of valve assemblies 5 and 7 are mounted on the manifold M as shown in FIG I. The valve 5 is a two position four-way valve having a first pair of ports 9 and I 1 opening into the manifold and a second pair of ports I3 and IS leading into the manifold. The port 9 is connected to a passage I7 in the manifold which leads to a port 19 opening to the pump pressure output while the port II is connected by a passage 21 to a port 23 opening to the pump return. The second set of ports I3 and of the valve open to passages 25 and 27 respectively in the manifold which in turn connect to ports 29 and 31 opening to the second valve 7. The valve 5 has a first position shown in FIG. 3 wherein the ports 9 and 11 are connected whereby the output from pump P is returned directly to the pump. The second position of valve 5 obtained by actuation of a solenoid 33 connects port 9 with 13 and port 11 with 15.

The second valve 7 which constitutes the direction valve is also a two position fourway valve having the previously referred to ports 29 and 31 as well as a second pair of ports 35 and 37 opening into the manifold and passages 39 and 41 respectively in the manifold. The passages 39 and 4I are connected to ports 43 and 45 to which the hydraulic driven actuator A is connected. The actuator A is connected to the main assembly by high pressure lines. The valve 7 is operated be tween its two positions by solenoids but is held by suitable detcnt mechanism indicated in FIG. 3 at 46 in a selected one of its positions until moved to the other position by actuation of one of the solenoids. In the first position shown in FIG. 3, the ports 29 and 35 are com nected and ports 3] and 37 are connected. In the second position, the ports are cross connected with port 31 connected to 35 and port 29 to 37. It will be clear that the actuator A will be driven selectively in two directions depending on the position of valve 7 and will continue to be driven in that direction whenever pressure is available at port 29 until the respective solenoid is actuated to move valve 7 into its other position.

The manifold M may have a bore 47 formed therein which interrupts passage 2] and in which a filter cartridge may be inserted to filter oil returning to the pump. Also relief valves 49 and SI seen in FIG. I are attached to the manifold to openings indicated at 53 and SS in FIG. 2 which interconnect passages 39 and 41, respectively. to limit pressure therein and also limit pressure in the actuator A.

In operation the displacement control 1 of the pump P is set for the required output. To begin drive the valve 7 is actuated to provide drive in the proper direction by actuation of one or the other of its solenoids. The valve 5 is then actuated to connect the pump to the second valve 7 and the actuator is driven in the proper direc tion. When the actuator A is connected to a machine component that is operable in opposite directions dur ing different parts of a machine cycle. at some point in that cycle the other solenoid is actuated to move the valve 7 to its other position changing the direction of drive. In the event that there is a stoppage or power failure the valve 5 will move to its off position shown in FIG. 3 but the valve 7 will remain in its then existing position. Upon reapplication of power the valve 5 will again be opened and the actuator A will be driven in the same direction as before the power cut-off.

It will be seen that l have provided a hydrostatic drive control that is compact. can be factory assembled and tested as a complete unit. will have a minimum of leak age and can be operated by one operator at one location. Modifications and changes will be apparent to those skilled in the art and such modifications and changes are deemed to be within the scope of the in vention which is limited only by the following claims:

I claim:

1. A manifold and integral valve assembly for a hydrostatic drive system that includes a pump and an actuator, said assembly including a manifold having first and second valve assemblies attached thereto. the first of the valve assemblies comprising a first two position four-way valve and the second of the valve assemblies comprising a second two position four-way valve, a first pair of passages in the manifold operatively connecting a set of pump ports in the manifold with a first pair of ports opening to the first valve assembly. a second pair of passages in the manifold connecting a second pair of ports opening to the second valve assembly. a third pair of passages in the manifold operatively connecting a second pair of ports opening to the second valve assembly with a pair of actuator ports, said first founway valve having a first position wherein its first pair of ports are interconnected and a second position wherein its first pair of ports are connected to its second pair.

the second four-way valve having a first position wherein its first and second pair of ports are connected (it I in one way to direct oil to and from an actuator to drive it in one direction and a second position wherein the first and second pairs of ports are connected in a second way to direct oil to and from an actuator in an op positc direction, operating means to move said second valve to one or the other of its positions, means to hold said second valve in either of its positions until said operating means moves the second valve to its other position. and means to move said first valve between its two positions to either direct oil to the second valve or back to the pump.

2. The manifold and integral valve assembly of claim I wherein said operating means for said second valve comprises a pair of solenoids and wherein said operating means for said first valve comprises a solenoid.

3. The manifold and integral valve assembly of claim I wherein a pair of relief valves are attached to the manifold and are connected to the third set of passages connected to the actuator ports. said relief valves act ing to limit the pressure in said actuator.

4. The manifold and integral valve assembly of claim l wherein a variable displacement pump is attached di rcctly to the manifold and has its output and return di rcctly connected to the pump ports in said manifold. 

1. A manifold and integral valve assembly for a hydrostatic drive system that includes a pump and an actuator, said assembly including a manifold having first and second valve assemblies attached thereto. the first of the valve assemblies comprising a first two position four-way valve and the second of the valve assemblies comprising a second two position four-way valve, a first pair of passages in the manifold operatively connecting a set of pump ports in the manifold with a first pair of ports opening to the first valve assembly, a second pair of passages in the manifold connecting a second pair of ports opening to the second valve assembly, a third pair of passages in the manifold operatively connecting a second pair of ports opening to the second valve assembly with a pair of actuator ports, said first four-way valve having a first position wherein its first pair of ports are interconnected and a second position wherein its first pair of ports are connected to its second pair, the second fourway valve having a first position wherein its first and second pair of ports are connected in one way to direct oil to and from an actuator to drive it in one direction and a second position wherein the first and second pairs of ports are connected in a second way to direct oil to and from an actuator in an opposite direction, operating means to move said second valve to one or the other of its positions, means to hold said second valve in either of its positions until said operating means moves the second valve to its other position, and means to move said first valve between its two positions to either direct oil to the second valve or back to the pump.
 2. The manifold and integral valve assembly of claim 1 wherein said operating means for said second valve comprises a pair of solenoids and wherein said operating means for said first valve comprises a solenoid.
 3. The manifold and integral valve assembly of claim 1 wherein a pair of relief valves are attached to the manifold and are connected to the third set of passages connected to the actuator ports, said relief valves acting to limit the pressure in said actuator.
 4. The manifold and integral valve assembly of claim 1 wherein a variable displacement pump is attached directly to the manifold and has its output and return directly connected to the pump ports in said manifold. 